TABLE 1.

Functional classification of genes with high environmental variation

GO category	No. of genes	Between-pair variation	Within-pair variation
Extracellular region	440	1.896	5.940
Extracellular space	463	5.131	5.419
Muscle development	110	3.027	4.659
Ion transport	319	0.562	3.871
Hormone activity	101	4.541	3.730
Transport	408	1.383	3.522
Structural molecule activity	292	1.507	3.447
Muscle contraction	116	2.180	3.349
Lipid metabolism	245	0.119	3.213
Cell division	141	−0.945	3.108
Cell differentiation	300	1.966	3.094
Ion channel activity	112	0.449	3.091
Development	461	1.489	2.832
Proteolysis	463	2.960	2.691
Extracellular matrix (sensu Metazoa)	170	2.432	2.549
DNA replication	127	−1.991	2.539
Cell cycle	454	−3.949	2.476
Nervous system development	289	1.024	2.455
Potassium ion transport	154	1.611	2.453
Sensory perception	181	3.149	2.432
Inflammatory response	180	−0.791	2.424
Cytoskeleton	390	2.551	2.383
RNA polymerase II transcription factor activity	152	−1.026	2.307
Iron ion binding	215	0.815	2.296
Sensory perception of sound	120	0.697	2.295
Cell–cell signaling	317	3.636	2.260
Visual perception	161	4.177	2.163
Positive regulation of cell proliferation	139	0.177	2.154
Regulation of transcription from RNA polymerase II promoter	205	−3.425	2.013

Listed are the GO categories with z > 2.0 (for environmental variation) having >100 genes, sorted by the environmental z-scores. The full list can be found in supplemental Table 1 at http://www.genetics.org/supplemental/. The GO categories were further grouped into four higher categories as follows: response to external signals (boldface type), cell differentiation and development (italics), cell division and proliferation (underline), and cellular transport (double underline).